Accessing biochar's porosity using a new low field NMR approach and its impacts on the retention of highly mobile herbicides.

Agrowaste biochars [sugarcane straw (SS), rice husk (RH), poultry manure (PM), and sawdust (SW)] were synthesized at different pyrolysis temperatures (350, 450, 550, and 650 °C) to evaluate their potential to retain highly mobile herbicides, such as hexazinone and tebuthiuron that often contaminate water resources around sugarcane plantations. A new low field nuclear magnetic resonance approach based on decay due to diffusion in internal magnetic field (NMR-DDIF) was successfully used to determine biochar's porosity and specific surface area (SSA) to clear the findings of this work. SSA of pores with diameters >5.0 µm increased with pyrolysis temperatures and seemed to dictate biochar's retention, which was >70% of the applied amounts at 650 °C. These macropores appear to act as main arteries for herbicide intra-particle diffusion into smaller pores, thus enhancing herbicides retention. Biochar granulometry had little, but herbicide aging had a significant effect on sorption, mainly of tebuthiuron. However, soils amended with 10,000 kg ha-1 of the biochars showed low sorption potential. Therefore, higher than usual biochar rates or proper incorporation strategies, i.e., surface incorporation, will be needed to remediate areas contaminated with these highly mobile herbicides, thus precluding their leaching to groundwaters.

Optimizing pyrolysis conditions for recycling pig bones into phosphate fertilizer.

Selecting pyrolysis parameters for recycling P-rich and hazardous biowastes, such as bones, into fertilizers is still a challenge. Our objective was to improve pyrolysis procedures of pig bones for the production of P fertilizers. Bone chars were produced by pyrolysis at 400, 550, or 800 °C with no gas addition; 550 and 800 °C under N2; 800 °C under steam flux, using calcination at 800 °C as control treatment. Synchrotron-based X-ray diffraction and X-ray absorption near edge structure spectroscopy at the P and Ca K- and L-edges showed that these bone chars were largely composed of hydroxyapatite. Hydroxyapatite crystallization was inhibited by pyrolysis conducted in the absence of oxygen at 400, 550, or 800 °C, either under no gas or under N2 flux. The clogging of pores by lack of organic compounds removal was hypothesized to cause low surface area of 400 °C bone char, resulting in a fertilizer with citric-acid soluble P as low as calcination, while 550 and 800 °C bone chars obtained in absence of oxygen showed greater porosity, surface area, and citric acid-soluble P than steamed or calcined samples at 800 °C. Although extractable phosphate in water and neutral-ammonium-citrate showed trends comparable to those from citric acid, it was negligible for all heated materials. Since it is possible to produce bone chars with different chemical, physical and crystallographic properties by managing pyrolysis conditions, bone chars can be designed to increase their suitability as P fertilizers for different purposes, such as high solubility or slow P release.

Polycyclic aromatic hydrocarbons in biochar amended soils: Long-term experiments in Brazilian tropical areas.

The interest in charcoal for agricultural use (biochar) has sharply increased in recent years. However, biochar can contain groups of compounds such as polycyclic aromatic hydrocarbons (PAHs) that are considered persistent pollutants, and are formed concomitantly with biochar during its production by pyrolysis. Soil samples were collected in three experimental areas at different intervals (1, 3, 5 or 6 years) after the application of 16 Mg ha-1 of biochar. The total concentrations of PAHs; benzo[a]pyrene; and the estimated total cancer risk in biochar treated plots were larger than found in the control ones, but they decreased over time, equaling the control values after three years in the high C content soil (11.2 g C kg-1 soil), or after six years in the low C content soil (6.8 g C kg-1 soil). Nevertheless, the sum of PAH concentrations found in the biochar amended plots, in the range of 15.80-39.40 ng g-1, were around two orders of magnitude below the limits of prevention established by Brazilian legislation (8100 ng g-1) and some European regulations for soils (3000 ng g-1) and also lower than the observed in previous studies about biochar amended soils. Our results indicate that, under the conditions evaluated, the application of biochar to soil in the studied proportion (16 Mg ha-1, every six years) is safe concerning soil contamination by PAHs.

Tracking thermal degradation on passion fruit juice through Nuclear Magnetic Resonance and chemometrics.

Thermal food processing mainly aims to control microorganism in order to extend its shelf life. However, it may induce chemical and nutritional changes in foodstuff. The Nuclear Magnetic Resonance (NMR) coupled to multivariate analysis was used to evaluate the effect of different thermal processing conditions (85 and 140°C for 4; 15; 30; and 60s) on the passion fruit juice using an Armfield pasteurizer. Through this approach it was possible to identify the changes in the juice composition. The temperature and the time lead to a hydrolysis of the sucrose to glucose and fructose. Additionally, juice submitted to 140°C for 60s results in the degradation of the sucrose and the formation of 5-(hydroxymethyl)-2-furfural (HMF). Despite no novel chemical marker has been identified, the 1H NMR chemometrics approach may contribute in the choice of the temperature and time to be employed in the juice processing.

Processed vs. non-processed biowastes for agriculture: effects of post-harvest tomato plants and biochar on radish growth, chlorophyll content and protein production.

The aim of this work was to address the issue of processed vs. non-processed biowastes for agriculture, by comparing materials widely differing for the amount of process energy consumption. Thus, residual post harvest tomato plants (TP), the TP hydrolysates obtained at pH 13 and 60 °C, and two known biochar products obtained by 650 °C pyrolysis were prepared. All products were characterized and used in a cultivation of radish plants. The chemical composition and molecular nature of the materials was investigated by solid state 13C NMR spectrometry, elemental analysis and potentiometric titration. The plants were analysed for growth and content of chlorophyll, carotenoids and soluble proteins. The results show that the TP and the alkaline hydrolysates contain lignin, hemicellulose, protein, peptide and/or amino acids moieties, and several mineral elements. The biochar samples contain also similar mineral elements, but the organic fraction is characterized mainly by fused aromatic rings. All materials had a positive effect on radish growth, mainly on the diameter of roots. The best performances in terms of plant growth were given by miscanthus originated biochar and TP. The most significant effect was the enhancement of soluble protein content in the plants treated with the lowest energy consumption non processed TP. The significance of these findings for agriculture and the environment is discussed.

Molecular characteristics of humic acids isolated from vermicomposts and their relationship to bioactivity.

Vermitechnology is an effective composting method, which transforms biomass into nutrient-rich organic fertilizer. Mature vermicompost is a renewable organic product containing humic substances with high biological activity. The aim of this study was to assess the chemical characteristics and the bioactivity of humic acids isolated from different vermicomposts produced with either cattle manure, sugar cane bagasse, sunflower cake from seed oil extraction, or filter cake from a sugar cane factory. More than 200 different molecules were found, and it was possible to identify chemical markers on humic acids according to the nature of the organic source. The large hydrophobic character of humic extracts and the preservation of altered lignin derivatives confer to humic acids the ability to induce lateral root emergence in maize seedlings. Humic acid-like substances extracted from plant biomass residues represent an additional valuable product of vermicomposting that can be used as a plant growth promoter.

A rapid and automated low resolution NMR method to analyze oil quality in intact oilseeds.

Oilseeds with modified fatty acid profiles have been the genetic alternative for high quality vegetable oil for food and biodiesel applications. They can provide stable, functional oils for the food industry, without the hydrogenation process that produces trans-fatty acid, which has been linked to cardiovascular disease. High yield and high quality oilseeds are also necessary for the success of biodiesel programs, as polyunsaturated or saturated fatty acid oil produces biofuel with undesirable properties. In this paper, a rapid and automated low resolution NMR method to select intact oilseeds with a modified fatty acid profile is introduced, based on 1H transverse relaxation time (T2). The T2 weighted NMR signal, obtained by a CPMG pulse sequence and processed by chemometric methods was able to determine the oil quality in intact seeds by its fatty composition, cetane number, iodine value and kinematic viscosity with a correlation coefficient r > 0.9. The automated system has the potential to analyze more than 1000 samples per hour and is a powerful tool to speed up the selection of high quality oilseeds for food and biodiesel applications.

Fracionamento químico da matéria orgânica e características de ácidos húmicos de solos com horizonte a antrópico da amazônia (Terra Preta) / Chemical fractionation of organic matter and humic acid characteristic in anthropogenic dark earth soils of brazilian amazonic region

Os solos da Amazônia que possuem horizonte A antrópico (Au) apresentam elevada fertilidade natural geralmente atribuída ao teor elevado de matéria orgânica e à sua elevada reatividade. Neste estudo foram quantificadas as substâncias húmicas e caracterizados os ácidos húmicos (AH) extraídos da camada 0-20 cm de solos com horizonte Au do estado do Amazonas (Terra Preta de índio) sob floresta e cultivo agrícola. Também foram investigadas amostras de solos adjacentes sem o horizonte antrópico. A caracterização dos AH foi realizada através de análise termogravimétrica, análise da composição elementar e quantificação dos grupos funcionais (total, carboxílica e fenólica). Os horizontes A de solos antropogênicos apresentaram maior teor de carbono total, comparados aos de solos adjacentes. Entre as frações húmicas, a mais abundante foi a humina. A fração de ácidos húmicos (AH) foi a dominante das frações alcalino-solúveis nos solos estudados. Os AH dos solos antropogênicos tanto sob floresta como sob cultivo agrícola apresentaram maior grau de humificação quando comparados aos AH dos solos sem o horizonte Au. O cultivo agrícola também teve efeito na estabilidade e reatividade dos AH nos solos antropogênicos.

Amazonian dark earth soils that have anthropogenic A horizon (Au) present high natural fertility usually attributed to their high organic matter content and to their higher reactivity. In this study humic substances were quantified and the humic acids (HA) extracted from the 0-20 cm layer of Amazonian dark earth soils (Terra Preta do índio) under forest and agricultural use were characterized. Adjacent soils with no Au horizon were also investigated. The HA were characterized through the thermogravimetric analysis, elemental composition analysis and characterization of functional groups (total, carboxylic, and phenolic). The A horizon of the anthropogenic soils presented higher total carbon level compared to adjacent soils. Among the humic fractions, the humin was the most abundant. The humic acid fraction (HA) was the dominant among the alkaline soluble fractions. The humic acids of the anthropogenic soils, both under forest and cultivation, showed higher humification degree compared to the non-anthropogenic soils. The agricultural cultivation affected the humic acids stability and reactivity in the anthropogenic soils.